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New scientific highlights- by MUST PIs Chergui, Milne and Wörner
New scientific highlights- from MUST researchers at PSI
Promotion to full professorcongratulations to Steve Johnson!
The Laser at 60: Ursula KellerOPN interviewed OSA Fellows
Former EPFL PhD student Edoardo Baldini wins the 2020 ACS PHYS Division Young Investigator Awards
New scientific highlights- by MUST PIs Banerji, Chergui and Wolf
Prix de l'innovation AGROVINA 2020- for Agrolase: detecting spores of pathogens in real time
Ruth Signorell receives the Humboldt Prize- awarded in recognition of outstanding achievements in research and teaching

Ultrafast Transient Increase of Oxygen Octahedral Rotations in a Perovskite

August 9, 2019  (more to follow)

Via femtosecond hard x-ray diffraction we identified a perovskite system that complements the rare selection of materials in which a symmetry broken phase can be transiently stabilized by photoexcitation. EuTiO3 exhibits a second order purely structural phase transition (TC = 290 K) which is characterized by an antiferrodistortive rotation of the oxygen octahedra (see figure, left unit cell) with the rotation angle being the order parameter. We directly monitor this angle upon photoexcitation across the band gap (data points) via x-ray pulses obtained from a FEL. Within the first few-hundred femtoseconds after excitation we observe a transient increase of rotation angle. This stands in contrast to the situation of an increased temperature for which the order parameter decreases. We ascribe the surprising increase of the order parameter to a transient effective change of ionic sizes that transforms directly into an ultrafast change of the Goldschmidt tolerance factor. The ability to modify the Goldschmidt tolerance factor provides another tuning parameter to control electronic and magnetic properties of perovskites on ultrafast timescales.

Reference: M. Porer, M. Fechner, M. Kubli, M.J. Neugebauer, S. Parchenko, V. Espositio, A. Narayan, N. A. Spaldin, R. Huber, M. Radovic, E. M. Bothschafter, J. M. Glownia, T. Sato, S. Song, S. L. Johnson, and U. Staub.
Phys. Rev. Research 1. 012005 (R) (2019). DOI: 10.1103/PhysRevResearch.1.01005
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